1. Field of Invention
The present invention relates to an electro-optical device, a driving method therefor, and an electronic apparatus.
2. Description of Related Art
In recent years, attention has been given to displays that have electro-optical elements, such as liquid-crystal elements, organic EL elements, electrophoresis elements, and electron emission elements, to serve as electro-optical devices.
One example of an active-matrix-drive system display is an organic EL display that uses organic EL elements as electro-optical elements. With an organic EL display, since the organic EL elements thereof serve as current drive elements, the total amount of light emitted by the display, i.e., the total brightness of the organic EL elements, is proportional to a power-supply current supplied to the pixels. Thus, controlling the level of the power-supply current allows the total amount of light emitted by the display to be controlled.
For example, an organic EL display that has a brightness limiting circuit for limiting the current level of the power-supply current supplied at the cathodes of the organic EL elements is known. FIG. 8 is an electrical block diagram of the known organic EL display. In an organic EL display 80 shown in FIG. 8, a brightness limiting circuit 81 is connected to the cathodes of organic EL elements 83 provided in pixels 82. The brightness limiting circuit 81 is configured with a resistance element Rg.
For example, when a data-line drive circuit 84 supplies a data signal VD having a large signal level to the corresponding pixels 82, a potential drop at the resistance element Rg becomes large by an amount corresponding to the signal level. A voltage between the drain and the source of a drive transistor Td of each pixel 82 decreases, as the potential drop at the resistance element Rg becomes large. Thus, the current level of power-supply current Io is limited correspondingly. The power-supply current Io is proportional to drive current supplied to the organic EL elements 83. Thus, when the power-supply current Io is limited, the current level of drive current Iel decreases correspondingly. As a result, the brightness of the organic EL elements 83 decreases.
When a data-line drive circuit 84 supplies a data signal VD having a small signal level to the organic EL elements 83, a potential drop at the resistance element Rg becomes small by an amount corresponding to the signal level. Thus, the power-supply current Io is output without limitation in accordance with a power-supply voltage VOEL. As a result, the voltage between the drain and the source of the drive transistor Td of each pixel 82 increases, so that the brightness of the organic EL element 83 increases (Patent Document 1).
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2002-132218